Method for reducing sliding friction



July 20, 1965 A. TUMA 3,195,428

METHOD FOR REDUCING sunme FRICTION Filed Jan. 31, 1963 Fig.1

INVENTOR Alex 771/770,

BY W WWW ATTORNEYS United States Patent 3,195,428 METHOD FOR REDUEIING SLIDING FRICTION Alex Turna, Loddekopinge, Sweden, assignor to AB Tetra, Lund, Sweden, 2 company of Sweden Filed Jan. 31, 1963, Ser. No. 255,293 Claims priority, application Sweden, Feb. 3, 1962, 1,198/ 62 1 Claim. (Cl. 9394) The present invention relates to a method for reducing the friction when a surface of thermoplastic material, for instance wax, paraffin or similar materials, is sliding against a metal surface.

For a long time it has been known to reduce the sliding friction between two surfaces by applying a lubricant between them. These lubricants normally have a liquid consistency, and otherwise they should have such qualities that they form a film between the two surfaces sliding against each other.

When a paper web coated with thermoplastic material is required to be converted into tubular shape, this is normally done by passing the paper web through one or more forming rings, where it acquires an outer configuration which is determined by the inner configuration of the ring. As the paper web during the forming operation is being pressed against the insides of the rings, a not inconsiderable amount of friction occurs between the rings and the paper web coated with thermoplastic material. This friction means not only that more energy is required for the forming, but also that the formed tube may become deformed owing to the tension stresses or in extreme cases it may get torn off.

These disadvantages associated with the sliding between a metal surface and a thermoplastic material are avoided by a procedure in accordance with the present invention, which is characterized therein that the metal surface is heated to a temperature which is higher than the melting point for the thermoplastic coating material, whereby the surface of the coating material as it comes into contact with the metal surface, is melted and given a low, frictionreducing viscosity in the contact area between the two surfaces sliding against each other, whereafter it again solidifies and form an even and tight surface, when the hot metal surface is removed.

A procedure in accordance with the invention, applied to conversion into a tubular shape of a paraffin coated paper web in the way above mentioned, is described in the following with reference to the enclosed diagrammatical drawing, in which FIG. 1 shows how a parafiin coated paper web when converted is drawn through a forming ring and FIG. 2 shows a cut-away of the forming ring as well as the paper web coated with paraffin.

The web I intended for conversion into tubular form consists of a paper carrier base 7 and a coating of for instance wax or paraflin applied to the base. The forming ring 3, which is seen to have a circular cross-section thereby to establish an inner curvilinear surface providing an essentially line contact with the paraffin coating 5, is provided internally with an electric heater core 6, which is connected to a source of current at the connection termirials 4. When the web 1, coated in this way with paraflin is passed through the forming ring 3, with the paraffin 3,195,428 Patented July 20, 1965 coating 5 in sliding contact with the inner surface of the ring, a very thin surface layer of the paraffin coating is melted under the forming ring 3 and immediately outside it. The heat supply to the forming ring 3 must be so adjusted that the surface of the coating 5 on the one hand becomes sufliciently fluid to reduce the friction, whilst on the other hand it must not be heated to a point where the whole coating 5 will liquefy as to impregnate the paper web or where it is chemically changed, for instance carbonizes.

The web 1 coated with paraffin is passed continuously through the forming ring 3 and consequently new coating material is steadily fed forwardly to the heated metal ring Where only the surface layer of the coating 5 is melted. The coating material, being melted on the surface and being carried forward together with the web 1 now converted into a tube 2, is carried forward after passing the heated forming rings, and thereafter cooled, whereby it solidifies and forms an even and tight surface coating. When the paraflln coating 5 is applied on the paper web 1, this is effected by a method, which is similar to a printing procedure. The method has the advantage that the coating material is applied in a semi-melted condition, whereby running parafiin is avoided. Further the thickness of the coating 5 may be controlled with greater accuracy than when melted paraflin is sprayed against the paper surface. The disadvantage with this coating method is, however, that the coating 5 does not become quite continuous and tight, wherefore dampness may penetrate through to the surface of the paper. After the Web 1 has been passed through the forming ring 3, and the surface layer of the parafiin coating 5 thus has been melted, a tight surface layer is formed after solidifying of the coating 5, which prevents dampness from penetrating to the paper web 1.

I claim:

In the method for converting a paper web coated with a thermoplastic material into a tube andwherein the thermoplastic coating is located on that face of the web which is to form the exterior surface of the tube, the improvement which comprises the steps of bringing the longitudinally extending edge portions of the thermoplastic coated paper web together with a metallic tube forming ring which has an inner curvilinear surface providing an essentially line sliding contact with the thermoplastic coated face of the web as the web is passed longitudinally through the forming tube, and heating said ring to such a temperature that the inner curvilinear surface thereof effects a temporay fusion of only the surface layers of said thermoplastic coating and a reduction in the sliding friction factor as between said coating and ring.

References Cited by the Examiner UNITED STATES PATENTS 1,913,447 6/33 Huston et al 93-80 2,105,273 1/38 Smith 9382 2,422,188 6/47 Epstein 9382 3,042,103 7/62 McDevitt et al 9382 3,063,860 11/62 Gemmer.

FRANK E. BAILEY, Primary Examiner.

ARTHUR M. HORTON, WHITMORE A. WILTZ,

Examiners. 

